Self-test arrangement for an entertainment-service system

ABSTRACT

In an entertainment-service system for permitting each of a plurality of local stations to select one or more of a plurality of channels of audio signals and to control one or more utilization circuits associated with each local station or group of such stations through the application of multiplexing techniques, the improvement consisting of a self-test arrangement whereby a test signal of predetermined characteristics is applied to each input channel of the multiplexing means and a self-test circuit means is provided at each station to detect said test signal and to override the control for said utilization circuit to activate said utilization circuit in a unique mode.

United States Patent Greenberg Dec. 24, 1974 SELF-TEST ARRANGEMENT FORAN 3,378,817 4/1968 vm 340 171 R ENTERTAINMENT SERVICE SYSTEM 3,560,6702/1971 Heyes et a1. 179/l75.31 R 3,728,713 4/1973 Alten 340/331 [76]Inventor: David R. Greenberg, 16 Serpentine i gg Long Island PrimaryExaminerl(athleen H. Claffy Assistant ExaminerDouglas W. Olms [22]Filed: July 6, 1973 Attorney, Agent, or Firm-Blum, Moscovitz, Friedman &K 1 21 Appl.No.: 376,982 ap Related US. Application Data 57 ABSTRACT[60] g gz gl f i 1 i i g gb 31: In an entertainment-service system forpermitting each 2 6 6 I IS a w 0 e of a plurality of local stations toselect one or more of a plurality of channels of audio signals and tocontrol [52] U S Cl 179/175 340/171 R one or more utilization circuitsassociated with each [51] m H04r 29/00 local station or group of suchstations through the ap- Fieid 175 31 R plication of multiplexingtechniques, the improvement 179/2 A i 1 consisting of a self-testarrangement whereby a test WM i R 3 2 signal of predeterminedcharacteristics is applied to each input channel of the multiplexingmeans and a [56] References Cited self-test circuit means is provided ateach station to detect said test signal and to override the control forUNITED STATES PATENTS said utilization circuit to activate saidutilization cir- 3,150,359 9/1964 Hoey 340 331 Quit in a unique, mode,3,256,517 6/1966 Saltzberg et al. 340/226 3,283,316 11/1966 Beardmore etal. 340/171 R 5 Claims, 8 Drawing Figures 7; ,76 SERVICE @005? ml /70I79 /6/1 an LIGHT SW/RV-l "1 1 /8/ AND WP CAI/ME MEANS J Cour/20LTRANSDUCER TEANSOl/CER .ss/vss sews: (220 22 4/ F/LTEQ fizz-5A l 1 lFKOM 1 A26 I22 40044 AEJIl/LT/PIE 1 1 1 [/8 l.. -o J J E 0 /20 00/12(/27 1 SHEET 2 [IF 8 PATENTED DEC 2 4 I974 PATENTEB UECZMSH SHEEI 3 BF 8PATENTED DEC24 I974 SHEET 4 OF 8 SHEET 8 [IF 8 PATENTEU 55524 I974MQQEMW r I l I SELF-TEST ARRANGEMENT FOR AN ENTERTAINMENT-SERVICE SYSTEMThis is a continuation, of now abandoned application Ser. No. 152,645,filed June 14, 1971 which is a divisional of application Ser. No.800,941 filed Feb. 20, 1969.

BACKGROUND OF THE INVENTION This invention relates generally toentertainmentservice systems of the type applicable to a plurality ofremote stations such as might be found in aircraft. The testing of suchsystems generally requires the separate operation of each component.Thus, if the system included a plurality of demultiplexers eachservicing a group of remote stations, each of said stations beingprovided with a separate headset, the prior art method of testing such asystem would consist of individually listening at each headset to detectan audio input. Substantially all of the entertainment portion of such asystem would be tested in this manner provided that at least one of thechannel selection means in the system is set to each of the channels. Totest the service portion of such a system, it would be necessary toindividually operate the utilization control means at each station anddetect the results at the corresponding utilization circuit.

The above described testing method is extremely time consuming, a factorwhich is of particular importance where the conduct of a lengthy testwould substantially increase the down time of an otherwise availableaircraft.

SUMMARY OF THE INVENTION Generally speaking, in accordance with theinvention, a self-test arrangement for an entertainmentservice system isprovided. The entertainment-service system to which the self-testarrangement according to the invention is to be applied includes anentertainment portion wherein a plurality of channels of input aremultiplexed and transmitted as a single signal to a plurality ofremotely located demultiplexer' means which reconstruct the content ofthe input channels selected by a channel selector means associatedtherewith and transmit said reconstructed signal to a correspondingtransducer means. The service portion of the system to be testedincludes a plurality of remotely located utilization circuits, at leastone utilization control means associated with each of said utilizationcircuits and means for placing each of said utilization circuits in astate responsive to the state of its corresponding utilization controlmeans. The self-test arrangement consists of a multi-channel test signalgenerator connected to the multiplexing means to apply a test signal ofa predetermined characteristic to each input channel and at least oneself-test circuit means connected to the output of each demultiplexermeans to detect the presence of said test signal and to override, inresponse to said detector test signal, at least one utilization controlmeans to produce a unique state indication at said utilization controlmeans effective to operate the corresponding utilization circuit in aunique manner. The unique state indication may correspond to that whichwould be produced if the utilization control means were alternatelyturned on and off so so that the corresponding utilization circuits arealternately rendered operative and inoperative when said test signal isdetected.

The self-test circuit includes filter means adapted to pass a signal ofa frequency substantially identical to the frequency of the test signal,transducer sense means adapted to produce a further signal if thetransducer means coils are intact, an AND gate to receive the signals ofsaid filter means and transducer sense means and switch means tooverride the utilization control means in the manner described above.

Accordingly, it is an object of this invention to provide a testarrangement for an entertainment-service system which requires a minimumof additional test equipment and which permits the rapid testing of thesystem.

Another object of the invention is to provide a testing arrangement foran entertainment-service system which permits ready diagnosis of anydefects therein.

A further object of the invention is to provide a testing arrangementwhich permits the testing of an entertainment-service system through theinclusion of a compact testing module within each local control of saidsystem and appropriate signal test generators.

Another object of the invention is to provide a testing arrangement foran entertainment-service system which permits the simultaneous testingof substantially the entire system.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combination of elements and arrangement of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a schematic representation of one type entertainment-servicesystem according to the invention;

FIG. 2 is a schematic representation of the main multiplexer of saidentertainment-service system;

FIG. 3 is a schematic representation of the local demultiplexer of saidentertainment-service system;

FIG. 4 is a schematic representation of the local control of saidentertainment-service system including the self-test circuit for saidsystem;

FIG. 5 is a circuit diagram of one type of the self-test circuit of FIG.4;

FIG. 6 is a schematic representation of the column timer, supervisoryutilization circuit and supervisory control of entertainment-servicesystem;

FIG. 7 is a schematic representation of the local coder of saidentertainment-service system; and

FIG. 8 is a schematic representation of the local decoder and localutilization circuits of said entertainment-service system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, theentertainment-service system depicted utilizes multiplexing techniques,preferably of the pulse code modulation type, to permit a plurality oflocal stations to selectively receive one or more of a plurality ofchannels of audio signals and to control one or more utilizationcircuits associated with each local station or a group of such stations.Pulse code modulation is a form of time division multiplexing whereinthe time available to transmit a plurality of channels of information isdivided into a plurality of discrete intervals or frames which areassigned successively to each of said channels. Each channel of information to be transmitted is successively sampled and the analog valuethereof is converted to a digital pulse code. Each of said intervals orframes are in turn divided into time slots, one of said time slots beingassigned to each bit of the digital code. Further time slots can beassigned for the transmission of other information, if desired. In thismanner a plurality of channels of information may be transmitted over asingle line and reconstructed at the receiver to produce the pluralityof channels of information originally transmitted.

In particular, in the system according to the invention, an audio input10, for example having ten channels, feeds into a main multiplexer 12.Said main multiplexer originates the basic system timing, multiplexesthe input signals by sequentially sampling each of the channels andconverting the analog signals to digital form, and transmits, along line13, the resulting digital data along with clock and synchronizationsgiansl in the form of a train of pulses, to the zone submultiplexers14. In the embodiment shown in FIG. 1, five further channels of audioinput 16 are applied to each zone sub-multiplexer 14. Each of said zonesub-multiplexers function in a similar manner to main multiplexer 12 tomultiplex said five additional channels and to interleave the resultingdigitized multiplexed signal in the appropriate frames of the mainmultiplexer output signal. The timing sampling arrangements of said mainmultiplexer are adapted to provide the additional frames required ineach cycle to permit the addition of the further five channels of audioinput by each zone sub-multiplexer 14.

The output of each zone sub-multiplexer 14, which consists of fifteenchannels of multiplexed information is applied to a single line 17.Reconstruction of the multiplexed signal for the remotely locatedstations is performed by a plurality of local demultiplexers 18, each ofwhich taps its respective line 17, econstructs the multiplexed signalinto its component channels of analog audio signals and transmits to itscorresponding headsets 20 disposed at each remote station the particularchannel selected by the local control 22 (22A, 228 or 22C) associatedtherewith. In this manner, a plurality of audio channels are transmittedto a plurality of stations represented by local controls 22 and headsets20 associated therewith. Each of said stations can be remotely locatedrelative to the audio inputs and 16, main multiplexer 12 and zonesub-multiplexer 14, while requiring only a single channel forinformation transmission, and therefore a minimum of wiring. Despite theuse of a single channel for transmission, each local control 22 canselect one or a pair of said channels (as in the case of stereotransmissions) to provide the user at the remote station with anaccurate reproduction of the audio signal from the multi-channeled input10 and 16.

Local controls 22 are also adapted to permit each remote station tocontrol, through the application of multiplexing techniques, a localutilization circuit 24 (24A, 24B or 24C) associated therewith. Suchlocal utilization circuit might include, for example, service calllights, other forms of attention-attracting alarm means, or lamps forgeneral illumination or reading.

For this purpose, column timer 26, a plurality of local coders 28 (28A28B, 28K) and a corresponding number of local decoders 30 (30A, 30B, T30K) are provided. Column timer 26 is adapted to produce the basictiming for this portion of the system, transmitting a clock andsynchronization signal alon data line 32 which interconnects said localcoders.

Each cycle is divided into frames, one frame being alloted to each localcoder-decoder pair. Each frame is in turn divided into time slotsallocated to each function to be performed such as the state of theportion of local control 22A which governs the service call light inlocal utilization circuit 24A or the state of the portion of localcontrol 22C which governs the light in local utilization circuit 24C.Data is transmitted in the form of a train of pulses, the presence orabsence of a pulse in each time slot governing the correspondingfunction. Each of said local coders are identical and adapted, whenactivated, to detect the state of the local controls associatedtherewith and to transmit digital data identifying said state to dataline 32 during predetermined time slots and frames. In like manner, eachof said local decoders are identical and are adapted to query said dataline during predetermined time slots .and frames to detect the localcontrol state data transmitted by the corresponding local coder, and tooperate the local utilization circuits 24 associated therewith, so thatthey are disposed in accordance with the settings of local controls 22.

Activation of local coder 28 and local decoders 30 in the appropriatetime frames is accomplished in re sponse to the clock andsynchronization signal generated by column timer 26 which is alsotransmitted along shift lines 34 which connect said column time andlocal coders 28 in series and shift lines 36 which connects said columntimer and local decoders 30 in series. The signal transmitted alongshift lines 34 and 36 sequentially activates local coders 28 and localdecoders 30 respectively so that for example, only local coder 28B andits corresponding local decoder 308 are activated during the second timeframe, and therefore transmit and receive during that frame.

Column timer 26 may also be adapted to perform supervisory coder anddecoder functions by querying data line 32 at a predetermined time slotsto detect local control state data contained therein or the activationof a centrally located supervisory utilization circuit 38 and totransmit to said data line, during predetermined time slots, digitaldata representative of the state of a supervisory control 40.

The embodiment of the entertainment-service system according to theinvention shown in FIG. 1 incorporates zone sub-multiplexers 14 tointroduce further channels of audio input 16. Such furtherchannels wouldbe required if it were necessary to provide a number of channels ofunique audio input at each zone, as would be the case where moves werebeing projected at each zone and synchronization between sound track andfilm required separate transmission of said sound track at each zone.However, where such separate transmission is not required, the audioinput 16 and zone sub-multiplexers 14 may be dispensed with in theentertainment-service system according to the invention. In suchembodiments, local demultiplexers l8 would tap directly ofi line 13 toreceive the output of main multiplexer 12.

Further, in the embodiment of the system shown in FIG. 1, one columntimer 26 is provided for the group of local stations associated witheach zone. However, depending on the number of local stations, theswitching speed of the equipment, and the frequency with which eachstation must be scanned, a single column timer 26 may be utilized tocontrol all of the local coders 28 and local decoders 30 in the system,without regard to the zone in which they may fall. In the altemative,more than one column timer might be utilized to control the local coders28 and local decoders 30 in each zone, provided that each local coderand its corresponding local decoder are tied to only a single columntimer. As shown by dashed lines 8, each line 17 would be provided with acomplete set of local demultiplexers 18, local controls 22, local coders22, a column timer 26, etc.

Turning now to a more detailed discussion of the components of theentertainment-service system according to the invention, reference ishad to FIG. 2 which shows a schematic representation of the mainmultiplexer 12. The ten channels of audio input are applied to tenamplifiers and filters 42, the output of which is applied to anelectronic commutator 44. The timing for the audio portion of the systemis obtained from crystal clock oscillator 46 which is applied to systemcontrol logic and timing counters 48. Said system control logic andtiming counters control the operation of the main multiplexer byproviding the gating signals to insure proper synchronization andsequential timing of the components. Thus, ten lines 50 connects systemcontrol logic and timing counters 48 to commutator 44 to enable saidcommutator to sequentially sample each of the ten input channels duringa predetermined time frame. Since the entire system, as shown in FIG. 1,

would include channels, the system control logic and timing counterswould actually divide a single cycle into fifteen time frames, only tenof which are utilized by the commutator 44 of the main multiplexer. Theremaining five time frames are preserved for the five additionalchannels to be introduced by each zone submultiplexer 14. The number ofchannels of the embodiment shown in the drawings is given by way ofexample and not by way of limitation, the actual number of channels inan entertainment-service system according to the invention being amatter of selection.

During the frame that each channel is being sampled, the sampled signalis applied to sample and hold circuit 52 which is also controlled bysystem control logic and timing counters 48 through an enable line 53and a reset line 54. The held sample is applied through a driver 55 tocomparator 56 of analog to digital converter 58 of conventional design.The timing for analog to digital conversion is also controlled by systemcontrol logic and timing counters 48. In the embodiment shown, analog todigital conversion is performed by an 8-bit ladder network 60 whichgenerates a series of voltages for application to comparator 56 througha driver 62. Said voltages are matched by said comparator to the sampledaudio signal. The ladder network 60 is controlled by a conversionregister 64 whose operation is in turn governed by a conversion controllogic 66 responsive to system control logic and timing counters 48. Whencomparator 56 detects a match between the audio signal and the voltageoutput of the ladder network 60, a signal applied along line 68 toconversion control logic 66 causes conversion register 64 to transmitthe digital code corresponding to the matched voltage along line 69 todata output logic 70. Said data output logic assemblies the variouscomponents of the main multiplexer output signal with each bit in itsassigned time slot and transmits said output signal through lowimpedance driver 72 to line 13, shown as a coaxial cable, fortransmission to the various zone sub-multiplexers l4. Timing for dataoutput logic is also provided by system control logic and timingcounters 48 through data timing lines 73.

The output signal from main multiplexer 12 consists of a periodic clockand frame synchronization signal 1 having the digital data representingthe audio signal in each channel interleaved therein, and is in the formof a train of pulses. The clock and frame synchronization pulses areprovided directly to data and input logic 70 by system control logic andtiming counters 48 through clock and frame sync line 74.

In some applications, it is desirable to provide a single channel ofinput, the activation of which overrides the other channels so that onlythe content of that channel is transmitted to headsets 20 irrespectiveof the channel selected by local control 22. Thus, it would be desirableto have the channel set aside for a public address system function inthis manner. To this end, an override bit is transmitted by systemcontrol logic and timing counters 48 in an appropriate time slot in eachframe to data output logic 70, along line 77 for interleaving in theoutput pulse train. Said override bit is generated in response to theactivation of said predetermined channel as by P. A. selector switch 75.Upon detection of such override bits, local demultiplexers l8 transmitonly the channel assigned to the public address system.

Still a further feature of the main multiplexer accoding to theinvention is the provision of stereo/monaural selector switches 76.These selector switches introduce a stereo tag bit into a predeterminedtime slot of the frame assigned to the first of two adjacent channelscarrying the left and right components of a stereo signal. When localdemultiplexer 18 detects such a stereo tag, it will apply one of saidpair of channels to the left and the other to the right side of headset20, treating said two adjacent channels as a single channel for thepurpose of channel selection by local control 22. This feature greatlyincreases the flexibility of the system since no channels arepermanently dedicated to stereo transmission.

Each of the zone sub-multiplexers 14 operates in substantially the samemanner as main multiplexer 12. The frame synchronization and clocksignal utilized to regulate the system control logic and timing countersof the zone sub-multiplexers is stripped from the signal on line 13,although each of said zone sub-multiplexers can be provided with anauxiliary crystal clock oscillator, if desired, to provide a standbytiming source in case of failure of the main multiplexer. In otherrespects, the zone sub-multiplexers preferably include system controllogic and timing counters, commutator, sample and hold circuit, analogto digital converter and data output logic similar in function andstructure to the corresponding components of the main multiplexer butadapted to interleave the digitized lots corresponding to the fivechannels of audio input 16 in the appropriate frames and time slotsreserved therefore and to pass the thus modified signal from line 13 toits respective zone line 17, which is also preferably a coaxial cable.

The signal from each zone line 17 is tapped off by the correspondinglocal demultiplexers 18, a schematic representation of one of which isshown in FIG. 3. The signal tapped from line 17 is amplified by highimpedance amplifier 78 and applied to shaper 80 adapted to eliminate anyspurious signals. The frame synchronization and clock portions of thesignal are detected by sync and clock detector 82 which applies theseportions of the signal to the system control logic and timing counters84 which control the timing and operation of the remaining components ofthe local demultiplexer. The clock signal drives the counters and logicwhile the frame synchronization is used to lock the system timing tothat of Zone sub-multiplexer 14 and main multiplexer 12. The signal fromshaper 80 is also applied to the data input logic and conversion control86 of digital to analog converter 88. This signal includes,sequentially, the digitized instantaneous value of each of the inputchannels audio signal plus stereo tag bits, if any. As each data bit isreceived, the corresponding flip-flop in the conversion register 90 isset to that data bit condition which in turn sets the 8-bit digital toanalog ladder network 92 to the original sample audio values. Thisladder network analog voltage is applied through driver 94 to aplurality of sample and hold networks 96 (96A-1, 96A-2, 96B-l, 96B-2,96C-1, 96C-2) One of said sample and hold networks are associated witheach audio output circuit, two of said audio output circuits beingprovided for each station (headset 20 and local control 22), wherebyeach station is provided with full stereo capability.

The system control logic and timing counters 84 provide timing signalsthrough lines 98 to channel selection logic 100. Said channel selectionlogic also receives the sterio tag, if any, from the data input logicand conversion control 86 along line 102 to determine whether a singlechannel of information should be applied to both audio output circuitsassociated with a single station or whether one of a pair of adjacentchannels of information should be applied to each of said two audiooutput circuits to produce a stereo effect.

Each of said sample and hold circuits 96 drives an active low passfilter 104, which drives into an amplifier 106 connected at its outputto capacitor 108, which in turn is connected to the audio output line110. Each pair of audio output lines 110Al and 1l0A-2, 110B-1 and1103-2, and l10C-l and llC-2, are connected to one of said localcontrols 22 (22A, 22B and 22C respectively) which contain channelselection means and headset 20 which is operated by the signal from saidaudio output lines.

Channel selection logic 100 detects the setting of each local control 22by means of lines 112A, 1123 and 112C connected respectively to audiooutput lines lA-l, 1108-1 and 110C-1 in a manner to be described below.ln response to the signal from said lines 112A, 1128 and 112C, channelselection logic 100 gates each sample and hold circuit 96 into and outof operation during the time frame corresponding to the channel selectedat the respective local control. This gating signal is sent along samplelines 1l4A-1, l14A-2, ll4B-1, l14B-2, 1l4C-1 and 1l4C-2. Thus, if localcontrol 22A were set to select a stereo program, that fact would bedetected by channel selection logic 100 through line 112A. Based on thesystem timing derived along lines 98, said channel selection logic wouldgate sample and hold circuit 96A-1 to sample and hold the output ofamplifier94 during the time frame assigned to the first of the pair ofstereo channels selected while sample and hold circuit 96A-2 would begated to sample and hold during the time frame assigned to the second ofsaid pair of stereo channels. If a monaural channel is selected at localcontrol 22A, sample and hold circuits 96A-1 and 96A-2 would besimultaneously gated to sample and hold the output of amplifier 94during the same time frames, whereby the same audio signal istransmitted to both sides of headset 20.

Filters 104 are selected to pass only audio frequencies and to have asharp attenuation characteristic to produce an audio output. This audiooutput is applied along each audio output line to its correspondinglocal control 22.

A block diagram of one of local controls 22 is shown in FIG. 4. Thechannel selection means 116 of said local control consists of a singlepole multiple position rotary switch. Movable arm 118 of said switchselectively engages one of a plurality of fixed contacts 120 which areconnected through resistors 122 to ground. Said movable arm is connectedby means of line 123 to audio output line 110A-l, and therefor to line112A of local demultiplexer 18, which in turn is connected to channelselection logic 100 for the purpose of detecting the state of saidchannel selection means.

Audio output line 110Al is also connected to capacitor 124 which in turnis connected to the input of rheostat 125. Audio output line l10A-2 isconnected through capacitor 126 to the input of rheostat 127. The leftand right transducers, 128 and 130 respectively, shown schematically,are connected between the wipers of said rheostats and 127, respectivelyand ground. In this manner, the audio signal, whether stereo ormonaural, is applied to the coils of transducers 128 and which convertthe electrical signal to sound for application to headsets 20.Adjustment of the rheostats 125 and 127 adjusts the volume of the signalapplied to said headsets. Channel selection means 116 is shown in FIG. 4with a l2-position switch, in which case several of the 15 inputchannels of audio would be stereo pairs automatically selected by oneposition on said channel selection means.

Each of said resistors 122 are of a different value. The selectedresistor serves as a part of a voltage divider located within channelselection logic 100 of local demultiplexer 18. The output of saidvoltage divider is filtered to d-c within said channel selection logicwhich is prferably provided with a ramp sweep generator and comparator.When said comparator matches the output of said ramp sweep generatorwith the output of said voltage divider as determined by the setting ofmovable arm 118, the comparator activates logic circuitry within channelselection logic 100 which, preferably through a digital code, identifiesthe selected circuit. As mentioned above, channel selection logic 100 isadapted to detect the stereo tag, if any, in which case two adjacentchannels of stereo would be treated as a single program selected by asingle position of selection switch 116. The foregoing arrangementpermits the seat selection function to share one of each pair of audiooutput lines 110, thereby avoiding an additional cable extending betweeneach local demultiplexer l8 and its corresponding local control 22.

Turning now to the service portion of the system, an example of a columntimer 26 and the supervisory utilization circuit 38 and supervisorycontrol 40 associated therewith is shown in FIG. 6. Basic timing forthis portion of the system is obtained by crystal clock oscillator whichprovides a stable frequency source which drives timing counters 132 toproduce system clock and frame synchronization pulses and to govern theoperation of data output logic 134. Such clock and sync pulses areincluded in the train of pulses forming the output of data output logic134 which is transmitted along line 135 to driver 136. This outputsignal is applied to data line 32 and shift lines 34 and 36. Asdiscussed above, shift line 34 is connected to the first local coder 28Awhile shift line 36 is connected to the first local decoder 30A. Thisoutput signal is divided by the clock and sync pulses into a pluralityof frames, each assigned to a particular local coder and itscorresponding local decoder. Each of said frames is subdivided and timeslots therein are assigned to each of the functions to be performed bythe service system. The data in each time slot is generally applied bylocal coders 28 in response to the settings of the corresponding localcontrols 22. However, it is sometimes desired to provide supervisorycontrol functions at a contral location, in which case a supervisorycontrol circuit 40 of the type shown in FIG. 6 might be connected todata output logic 134, which would then interleave in the appropriatetime slots, as governed by timing counters 132, data responsive to thesettings of said supervisory control.

In the embodiment shown in the drawings, the service portion of thesystem is adapted by way of example, to perform two functions, namely toactivate a lamp associated with each local control and to activate aservice call light associated with each group of three local controls.The supervisory control shown in FIG. 6 serves both a test and afunctional purpose and consists of a three-position lamp test switch138, a twoposition service call light test switch and a service calllight reset switch 142. Lamp test switch 138 consists of movable arm 143adapted to engage any one of three contacts 144, and 146. When firstcontact 144 is engaged, data output logic 134 transmits the datarequired to turn all lamps in all local utilization circuits 24 on. Whensecond contact 145 is engaged, data output logic 134 interleaves thedata in the appropriate time slots of the output signal directing alllamps in all utilization circuits to be turned off, third contact 145being a neutral position.

Service call light test switch 140 includes a movable arm 146 normallyengaged to neutral fixed contact 147, but displaceable into engagementwith the other fixed contact 148, in which case data output logic 134will interleave into the pulse stream, the appropriate data necessary toactivate all service call lights of all of said local utilizationcircuits. Reset call light switch 142, when depressed, causes dataoutput logic 134 to interleave into the data stream in the appropriatetime slots the data necessary to reset all of the service call lamps ofall of said local utilization circuits. Also included are switches 166and 168 which control the test signal generators utilized in theself-test feature of the system in a manner to be described below.

The embodiment of the system shown in the drawings also includes asupervisory utilization circuit 38, which is shown in FIG. 6 to includea supervisory chime 150 and a supervisory call light 152. To this end,column timer 26 is preferably provided with data input logic 154 whichtaps data line 32 by means of line 156. The timing of said data inputlogic is governed by timing counters 132 through line 157. If data inputlogic 154 detects that any one of the local controls 22 is set to enableits corresponding call light in its corresponding utilization circuit tolight, a signal is passed along lines 158 to flip-flop 160, the outputof which is connected to supervisory call light 152 through amplifier162. F lip-flop 160 serves to latch the supervisory call light in the onposition until all of the call light controls in all of the localcontrols 22 are reset. The affirmative act of resetting is required toinsure that appropriate action is taken in response to each service calllight. As a further alarm means in connection with the service calllight, the activation of the service call light control at a localcontrol 22 also results in the transmission by the local coder in theappropriate time slot of a pulse directing the ringing of supervisorychime 150. This pulse is detected by data input logic 154 to pass asignal along line 163 to single shot multivibrator 164 the output ofwhich is connected to said supervisory chime through amplifier 165. Thefrequency and duty cycle of said single shot multivibrator 164 isselected to limit the frequency with which the chime rings.

' As shown in FIG. 4, each local control 22 includes a manual lampcontrol operative through switch means 174 to impress a signal on line176, which in turn in connected to its corresponding local coder 28.Similarly, each local control 22 is provided with service call light andchime control 178, which, when depressed, closes contacts 179 to passfirst signal along line 180 to said corresponding local coder, and whenraised, closes contacts 181 connected in series with resistance 182 topass a second, different, signal on line 180. Preferably, said firstsignal represents a command to light the corresponding service calllight and ring the supervisory chime, while said second signal directsthe resetting of said corresponding service call light.

As seen in FIG. 7, which schematically represents one example of a localcoder 28 according to the invention, lines 176 and 180 from the lampcontrol 170 and service call light and chime control 178 respectively ofeach local control 22A, 22B, 22C are applied to the date output logic183 thereof. Timing for local coders 28 is obtained by means of sync andclock detector 184, preferably a chain of single shot multivibrators,which taps off data line 32 and strips the clock pulses from the pulsetrain. The clock and frame synchronization pulses are passed to timingcounters 186 along clock and reset lines 185. Said timing counterscontrol the functioning of data output logic 183 through lines 187 butare inhibited from driving said data output logic until a shift-incommand is received from shift line 34 connected to the last localcoder, or in the case of the first local coder 28A, connected to thecolumn timer 26. This shift command consists merely of the sync andclock pulse and operates as follows. The frame synchronization pulseresets all of the timing counters 186 in all of the local coders 28A,28B, 28K, enabling the timing counters on the first local coder torespond to the clock pulses received from column timer 26 along shiftline 34. When the timing counters 186 of said first local coder 28A havecompleted their cycle and directed data output logic 183 thereof totransmit the state data of the corresponding local controls 22, ashift-out command is generated by said timing counters and passed alongshift line 34 to the timing counters of the second local coder 28B whichis then activated to function as described above. This sequentialactivation of the local coders continues until the last local coder 22Khas completed its cycle, at which time a frame synchronization pulseresets the entire portion of the system and a new cycle is commenced.

During the period that each local coder is activated, data output logic183 detects the states of local controls 22A, 22B and 22C and, duringappropriate time slots, transmits data representative of said statesthrough low impedance driver 188 to data line 32. The sequentialactivation of said local coders insures that the data is interleavedinto the proper frame for detection by the corresponding local decoder30.

Local coders 30, a schematic representation of one example of which isshown in FIG. 8, are designed to be sequentially activated in the samemanner as said local coders. Thus, the pulse train-is tapped off dataline 32 and applied through driver 190, to sync and clock detector 192and data input logic 194. Reset and clock pulses are applied from saidsync and clock detector to timing counters 195 which are governed byshift commands from shift lines 36. Sync and clock detector 192, timingcounters 195, and shift lines 36 function in the same manner as sync andclock detector 184, timing counters 186 and shift lines 34 of localcoders 22, and a detailed description of their operation will not berepeated at this point. The operation of data input logic 194 isgoverned by timing signals obtained from timing counters 195 along lines196.

In the embodiment shown in FIG. 8, the local utilization curcuits 24A,24B and 24C, have, in part, been combined to provide only a singleservice call light 200 for the three stations controlled by each localdecoder 30. Of course, this system according to the invention caninclude separate service call lights for each station, if desired.Further, said local utilization circuits include a lamp 202 (202A, 202Band 202C) for each station. Service call light 200 is driven throughdriver 204 and flip-flop 206 by data input logic 194. In like manner,each lamp 202 is driven through a bi-directional gatecontrolledthyristor which completes the A-C path for said reading lamp when gatedon, said gating signal being derived from flip-flop 210 controlled bydata input logic 194. The data input logic 194 of each local decoder isactivated in its proper time frame, detects the state data stored ineach time slot of that frame and transmits a signal to the specificservice call light on lamp of its utilization circuit 24 associated withsaid time slot to set the state of said call light or lamp. The group oflocal coders and the group of decoders are each in series connection forthe purposes of sequential shifting. The correct local code and decoderare simultaneously activated during each frame, for example, local coder28B and local decoder 30B.

The above-described arrangement permits both the local coders and localdecoders to be interchangeable among themselves since special circuitryis not required for each station to identify the local control orutilization circuit associated with that station, while fullmultiplexing is accomplished. This feature offers substantial advantagesin terms of the number of types of equipment that must be maintained oninventory and convenience of maintenance. Said local coders and decodersare preferably adapted to be bidirectional by providing appropriategating in timing counters 186 and 194 so that the system is operative ifthe column timer 26 were connected at the other end of the seriesconnection of said local coders and decoders. If the system alsoincorporates supervisory control 40, the system timing is adjusted sothat the data representative of the test functions and the supervisorycall reset are detected after the data from each local coder 28 islatched so that the supervisory inputs would override the local controlstate date in all cases. In view of the switching speeds contemplated,the time gap between a particular data bit from the local coder and theoverriding data bit from the supervisory control would be so slight asto be imperceptible.

While the supervisory control 40 provides some element of testcapability to the system, a device for testing substantially the entireentertainment-service system would offer substantial advantages. To thisend, a self-test circuit 220 is provided in each local control 22 asexemplified in FIG. 4, a ten-channel test signal generator issubstituted for audio input 10 and a fivechannel test signal issubstituted for audio input 16. Said test signal generators are adaptedto produce over eachof the system audio channels a test signal ofpredetermined characteristics not normally present in the audio inputsignal. The test signal is preferably a tone of a frequency within theaudio frequency range to pass filters 104 and of sufficient strength tooperate self-test circuit 220. The test signal generator may take any ofthe forms well known in the art and may be built into audio inputs 10and 16. In such case, as shown in FIGS. 1 and 6, supervisory control 40could be provided with switch 166 to remotely activate the ten channeltest signal generator in audio input 10 by means of lines 167 and switch168 to remotely activate the corresponding five channel test signalgenerator in audio input 16 by means of lines 169. The supervisorycontrol incorporated in each of the other assemblies 8 would onlyincorporate switch 166 to control the test generator incorporatedtherein.

In its simplest form, said self test circuit 220 is provided with afilter 222 connected to audio output line 1l0A-1 and filter 224connected to audio output line I l10A-2. These filters are selected topass only the frequency generated by said test signal generators and areconnected to AND" gate 226 the output of which is connected to switchmeans 174. In the embodiment shown, switch means 174 is connected tomanual lamp control 170 and adapted, in response to an output by ANDgate 226, to override said lamp control to produce a unique indicationon line 176 equivalent to the repetitive opening and closing of saidlamp control. If the entire system were operating properly, every lamp202 in the system would blink in response to the signal so generated. Tofurther extend the scope of the test on the system, self-test circuit220 preferably includes a first transducer sense means 228 connected tothe input side of transducer 128 and a second transducer sense means 230connected to the input side of transducer 130. Each of said transducersense means is adapted to provide an output to gate 226 when the coilthat the AND gate 226 for that particular local control is not actuatedand the corresponding lamp 202 does not blink.

If steps are taken to insure that at least one of each of the channelselector means 116 is set to each of the possible channels, the blinkingor failure to blink of lamps 202 provides a test of substantially all ofthe system.

Thus, since each AND gate 226 requires the proper functioning of the twoaudio input channels and the two transducer coils associated therewith,it is apparent that substantially all of the entertainment portion ofthe system, including the entire main multiplexer and zonesub-multiplexer and substantially all of the local demultiplexers aretested. Further, since the output of the gate is connected to theservice portion of the system, substantially all of the column timers,local coders, and local decoders are also tested. In this connection, itis noted that the lamps 202 are also tested and that the balance ofsupervisory utilization circuit 38 and service call light 200 would betested by the activation of the call light test switch 140 insupervisory control 40. Thus, by merely substituting test generators foraudio inputs l and 16 the system performs an automatic self test. Thisself test results in substantial savings in time and labor and alsoprovides a ready indication of the nature of any faults in the systemthrough an analysis of the particular lamps 202 which fail to blink.

Turning now to FIG. 5, a detailed circuit diagram of self-test circuit220 is shown. The power supply for said self-test circuit is provided bytapping off audio output line ll0A-2 and filtering the d-C componentfrom that output by means of resistor 240 and capacitor 241. Arectifying arrangement tapping off the audio output line can also beutilized. A positive voltage thus appears at terminal 242 and the biasvoltages for the remainder of the circuit are obtained by connecting tosaid terminal. Filters 222 and 224 are substantially identical,consisting of series connected capacitors 244 shunted to ground byresistors 246 to define a first filtering stage and diodes 248 andresistors 250 shunted to ground by capacitors 252 and resistors 256 todefine a second filtering stage. Transducer sense means 228 and 230 aredefined by series connected resistors 256 connected to the base oftransistors 258. The bases of said transistors are also connectedthrough resistors 260 to bias voltage terminal 242 and to ground throughcapacitors 261. The collectors of said transistors are connected throughresistors 262 to said bias voltage terminal while the emitters thereofare connected to ground. Transistors 258 are normally biased off.However, if a transducer coil is broken and a high impedance to groundappears at the input to transducer sense means 228 or 230, then thetransistor 258 of that transducer sense means will be forced intoconduction to close AND gate 226.

Said AND" gate consists of diodes 264 connected respectively at theircathodes to the output of transducer sense means 228 and 230 (thecollector of transistors 258), and resistor 270 connected at one end tothe anodes of diodes 264 and 266 and, at its other end, to the biasvoltage terminal 242. The output of AND" gate 226 is connected to theinput of switch means 174 represented by capacitor 270 shunted to groundand series connected resistor 272, which in turn is connected to theinput of astable multivibrator 274. Ca-

pacitor 270 provides a delay means for distinguishing the test signalfrom a portion of the regular audio input signal which might be of thetest signal frequency. Said test signal frequency is preferably chosenfrom among those frequencies least likely to be present in normal audioprogramming. The test signal must be present for sufficient time tocharge capacitor 270 to the triggering voltage of multivibrator 274,preferably about fifteen seconds. Said triggering voltage provides stilla further distinguishing characteristic of the test signal since a weaksignal will be insufficient to trigger the multivibrator, and thereforeto override the manual control of the corresponding lamp 202.

Said astable multivibrator includes transistors 276 and 277. The base oftransistor 276 is connected to the cathode of diode 278, the base ofwhich is connected through capacitor 279 to the collector of transistor277. In like manner, the base of transistor 277 is connected to thecathode of diode 280 which in turn is connected to the collector oftransistor 27 6 through capacitor 281. The base of transistors 276 and277 are connected respectively through resistors 282 and 283 to ground.The emitters of said transistors are connected together, said commonconnection being connected through resistor 284 to ground. Thecollectors of said transistors are each connected through a resistor 285and 286, respectively, to bias voltage terminal 242. The anode of diode280 is connected to said bias voltage terminal through resistor 287,while the anode of diode 278 serves as the input to said multivibrator.The output of said multivibrator is taken at the collector of transistor276 and is connected through resistor 288 to transistor 290.

The collector oftransistor 290 is connected to output line 176 leadingto the corresponding local coder. The emitter of said transistor isconnected through resistor 291 to bias voltage terminal 242 and throughresistor 292 to the movable arm of lamp control 170. Said movable arm isshunted to ground by means of resistor 293. The fixed terminal of lampcontrol is connected to the emitter of transistor 295, said emitter alsobeing connected to ground through resistor 296. The base of transistor295 is connected through resistor 297 to the output of gate 226. Thecollector of said transistor is connected to the aforementioned line 176which is shunted to ground by means of diode 298.

Switch means 174 operates as follows. When no test signal is detected,and the normal audio inputs [0 and 16 are applied, the manual closing oflamp control 170 turns on transistor 295 to present the appropriatesignal to line 176, and therefore to the local coder. If said lampcontrol is open, transistor 295 is turned off, also giving theappropriate indication to said local coder. Transistor 290 is in the offcondition during this mode since its base is returned to transistor 276of astable multivibrator 274 which is normally off.

If a test signal is applied by means of a test signal generator, thedetection of said test signal by the AND gate, assuming all componentsof the system are functioning properly, produces a d-c level atcapacitor 270 proportional to the amplitude of said test signal. Thispositive level is coupled through resistor 297 to the base of transistor295 to maintain said transistor in reverse biased condition for theduration of the test signal detection. This in effect disables thecontrol function of lamp control 170, the signal passed along line 176now being under the control of transistor 290 alone. This transistorfollows the voltage levels of transistor 276 of multivibrator 274,alternating conduction and nonconduction with transistor 277 in theknown manner. Accordingly, the signal at line 176 is an alternatingsignal which produces a blinking lamp in the corresponding utilizationcircuit to indicate a successful test. If a test signal is not detected,indicating some failure, the voltage of capacitor 270 is very nearlyzero and the return path for the base of transistor 290 is throughdiodes 264 and 266 and the resistive path upstream thereof. In thelatter case, the state of the lamp would be governed by lamp control 170and would be steady.

If the entertainment-service system includes the special channelgoverned by P. A. selector switch 75, the activation of which overridesall other channels to apply the contents of said special channel to allof the headsets without regard to the setting of channel selectorswitches 116, said special channel can be readily tested using thearrangement according to the invention. Testing can be accomplished byadapting the test signal generator to selectively apply a test signaldifferent from the normal test signal to said channel while the normaltest signal is applied to the balance of the channels. If the lamps 202stop blinking and return to their normal state, the override feature ofthe special channel is operating properly. This results from the factthat the signal on the special channel is applied to all of the audiooutput lines instead of the normal test signal. Said special test signalcan be of a different frequency which is not passed by filters 222 and224 or of insufficient strength to trigger multivibrator 274. A separateswitch can be provided in supevisory control 40 to apply the specialtest signal to the special channel after switches 166 and 168 areclosed.

Self-test circuit 220 is shown disposed in local control 22 but could bedisposed in either local coder 28 or local demultiplexer 18. While inthe embodiment shown, the self-test circuit is connected to overridelamp 202, this is merely shown by way of example and not limitation andany utilization circuit capable of indicating a successful test could beused for this purpose. Thus, service call lights 200 could be used asthe alarm. Further, the unique test state of the utilization circuitproviding test indication need not be the blinking state used in theembodiment shown. For example, if service call lights 200 are used andreset button 142 of supervisory control 40 is depressed before test, thelighting of said service call lights could provide the test indication.

The entertainment-service system according to the invention has manyapplications. For example, the system can be applied to an aircraft orother means of transportation where it is necessary for each seat toindividually control entertainment functions by selectively choosing aplurality of channels and service functions such as reading lamps andservice call lights to attract the attention of stewardesses. In such anapplication, the zone sub-multiplexers 14 might represent a compartmenton the aircraft, each local decoder, each local coder and localdemultiplexer being associated with a row of seats within thatcompartment, and each local utilization circuit and local control beingassociated with a particular seat within that row. Theentertainment-service system according to the invention is particularlyadvantageous for use in aircraft where weight considerations are ofcritical importance, since the multiplexing techniques used hereinresult in substantial savings in weight. Further, the self test circuitexpedites servicing time, therefore minimizing the down-time of anextremely valuable aircraft. Still other applications of the systemaccording to the invention include, but are not limited to use inhospitals, intercom systems in buildings and all other circumstanceswherein a plurality of remote stations are to be tied to a singleentertainment-service system.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description are efficiently obtained, and,since certain changes may be made in the above constructions withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention, which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. A self-test arrangement for connection in a system having an output,an input, lamp means normally in an illumination mode in which said lampmeans can provide illumination independent of any test function andcapable of serving as a test-result indicator when disposed in apredetermined test state, manual switch means for selectivelycontrolling said lamp means when said lamp means is in its illuminationmode by providing signals for turning said lamp means on and off, andsignal transmission means interconnecting said input, output and lampmeans for transmitting at least said signals for turning said lamp meanson and off when said lamp means is in said illumination mode comprising,means for selectively applying a test signal to said system input fortransmission through said signal transmission means to said output,filter means connected to said system output for passing only an outputsignal substantially equal to the frequency of said test signal appliedto said system input, and second switch means connected to said lampmeans through said signal transmission means and to said filter meansfor disposing said lamp means in said predetermined test state withoutregard to the state of said manual switch means in response to saidoutput signal from said filter means.

2. An arrangement as recited in claim 1, wherein said predeterminedalarm state of said lamp means is a blinking state, said switch meansincluding lamp blinking circuit means.

3. An arrangement as recited in claim 1, wherein said system includesaudio transducer means having at least one transducer coil and saidself-test arrangement includes AND gate means connected intermediatesaid filter means and switch means to receive the output signal of saidfilter means, transducer sense means connected to said transducer coiland adapted to produce a signal if said coil is unbroken, saidtransducer sense means being connected as a further input to said ANDgate means.

4. An arrangement as recited in claim 1, wherein said second switchmeans is adapted to dispose said utilization circuit in saidpredetermined state only if a predetermined period passes during whichsaid filter means output is applied thereto.

5. A self-test arrangement for connection to a system having a centralstation and a plurality of local stations, lamp means at each of saidlocal stations each normally in an illumination mode in which said lampmeans can provide illumination independent of any test function andcapable of serving as a test-result indicator when disposed in apredetermined test state; manual switch means at each said local stationfor selectively controlling the associated lamp means when said lampmeans are in their illumination mode by producing signals for turningsaid lamp means on and off; and signal transmission meansinterconnecting said control station and said local stations, and saidlocal stations and said lamp means for transmitting at least saidsignals for turning said lamp means on and off; comprising means forselectively applying a test signal to said signal transmission means atsaid central station; means for detecting said test signal at each ofsaid local stations and producing an output upon said detection; andmeans at each of said local stations connected to the associated lampmeans through said signal transmission means for disposing said lampmeans in said predetermined test state without regard to the state ofsaid manual switch means in response to said detecting means output.

1. A self-test arrangement for connection in a system having an output,an input, lamp means normally in an illumination mode in which said lampmeans can provide illumination independent of any test function andcapable of serving as a test-result indicator when disposed in apredetermined test state, manual switch means for selectivelycontrolling said lamp means when said lamp means is in its illuminationmode by providing signals for turning said lamp means on and off, andsignal transmission means interconnecting said input, output and Lampmeans for transmitting at least said signals for turning said lamp meanson and off when said lamp means is in said illumination mode comprising,means for selectively applying a test signal to said system input fortransmission through said signal transmission means to said output,filter means connected to said system output for passing only an outputsignal substantially equal to the frequency of said test signal appliedto said system input, and second switch means connected to said lampmeans through said signal transmission means and to said filter meansfor disposing said lamp means in said predetermined test state withoutregard to the state of said manual switch means in response to saidoutput signal from said filter means.
 2. An arrangement as recited inclaim 1, wherein said predetermined alarm state of said lamp means is ablinking state, said switch means including lamp blinking circuit means.3. An arrangement as recited in claim 1, wherein said system includesaudio transducer means having at least one transducer coil and saidself-test arrangement includes AND gate means connected intermediatesaid filter means and switch means to receive the output signal of saidfilter means, transducer sense means connected to said transducer coiland adapted to produce a signal if said coil is unbroken, saidtransducer sense means being connected as a further input to said''''AND'''' gate means.
 4. An arrangement as recited in claim 1, whereinsaid second switch means is adapted to dispose said utilization circuitin said predetermined state only if a predetermined period passes duringwhich said filter means output is applied thereto.
 5. A self-testarrangement for connection to a system having a central station and aplurality of local stations, lamp means at each of said local stationseach normally in an illumination mode in which said lamp means canprovide illumination independent of any test function and capable ofserving as a test-result indicator when disposed in a predetermined teststate; manual switch means at each said local station for selectivelycontrolling the associated lamp means when said lamp means are in theirillumination mode by producing signals for turning said lamp means onand off; and signal transmission means interconnecting said controlstation and said local stations, and said local stations and said lampmeans for transmitting at least said signals for turning said lamp meanson and off; comprising means for selectively applying a test signal tosaid signal transmission means at said central station; means fordetecting said test signal at each of said local stations and producingan output upon said detection; and means at each of said local stationsconnected to the associated lamp means through said signal transmissionmeans for disposing said lamp means in said predetermined test statewithout regard to the state of said manual switch means in response tosaid detecting means output.